The brand new HK MP5 series from Umarex is an amazing piece of engineering, and one of the highest quality airsoft replicas we've ever seen. Made by VFC, the HK MP5A4 and MP5A5 feature a stamped steel receiver, 4 position selector, and build quality to rival a real H&K. In this review, we'll look at some of the details, as well as check out the gearbox that makes this thing hum.